1. Field of the Invention
The present invention relates to a liquid droplet jetting apparatus and a liquid droplet jetting head.
2. Description of the Related Art
As a liquid droplet jetting apparatus, an ink-jet printer which includes a cavity unit in which a plurality of pressure chambers is arranged regularly, an ink-jet head in which a piezoelectric actuator for jetting an ink in the pressure chambers selectively is joined to the cavity unit, and a voltage applying mechanism which applies a voltage to the piezoelectric actuator has hitherto been known. Moreover, as the piezoelectric actuator described above, a longitudinal-effect actuator of a stacked type (refer to U.S. Pat. No. 7,073,894 B2, corresponding to Japanese Patent Application Laid-open No. 2005-59551 for example), and a unimorph actuator (refer to US2005/0231073 A1, corresponding to Japanese Patent Application Laid-open No. 2005-317952) have been known.
In an ink-jet head of such printer, a high densification of pressure chambers has been sought for securing a high quality and a high image quality of recording by increasing the number of nozzles. When the pressure chambers are arranged in a row highly densely, since a distance between the adjacent pressure chambers becomes short, an effect of the adjacent pressure chamber at the time of driving becomes substantial, thereby causing a problem of a so-called cross-talk.
An ink-jet head, as shown in FIGS. 14 and 15 for example, has a piezoelectric actuator 912 having three piezoelectric material layers 912a, 912b, and 912c, a cavity unit 940 in which pressure chambers 914a are arranged regularly, and a confining plate 115 which is joined between the cavity unit 914 and the piezoelectric actuator 912. Moreover, on an upper surface of the piezoelectric material layers 912a and 912c, individual electrodes 921 are formed corresponding to the pressure chambers 940, and on a lower surface of the piezoelectric material layers 912a and 912c, a constant electric potential electrode (a controlled (fixed) electric potential electrode) 922 (ground electric potential electrode 922) is formed. In this case, at the time of applying a positive electric potential (for example an electric potential of 20V) to the individual electrodes 921 selectively, areas of the piezoelectric material layer sandwiched between the individual electrodes 921 and the constant electric potential electrode 922 function as active portions S each of which makes jet the ink from a nozzle hole 914b by changing a volume of one of the pressure chambers 940. A deformation of the active portions S (piezoelectric material layers 912a to 912c) for such ink jetting affects not only the one of the pressure chambers 940 jetting the ink but also another pressure chamber 940 adjacent to the one of the pressure chambers 940.
Therefore, a defect such as a fluctuation in jetting characteristics of the adjacent pressure chamber 940 (such as an unintentional jetting of the ink from the nozzle hole 114b), in other words, the cross-talk has been occurring.
For solving a problem of such cross-talk, various measures have been proposed. For example, in a head described in Japanese Patent Application Laid-open No. 2002-254640 (FIG. 2), a beam portion 100 is provided between partition walls 11 on two sides in a width direction of a pressure generation chamber 12, and a stiffness of the partition walls 11 is improved. Accordingly, the cross-talk is prevented from occurring between the adjacent pressure generating chambers.
Moreover, in a head described in Japanese Patent Application Laid-open No. 2002-19113, an elastic body 7 is arranged in an area occupying a predetermined depth and a predetermined width from a nozzle plate 3, of a side wall 5 which demarcates each pressurized liquid chamber 4. Accordingly, a mechanical cross-talk is reduced.